This invention relates to devices for delivering breathing air to a user. Specifically, this invention relates to a breathing apparatus for use in toxic environments that delivers breathing air to a user through a mask which is maintained at a positive pressure.
Numerous types of devices for delivering breathing air to a user are known in the prior art. Such devices have different performance requirements depending on the circumstances in which they are intended to be used.
One critical application for air delivery devices are situations in which users are required to work in environments with toxic materials or gases. One group of workers who frequently are required to work under such conditions are firefighters. Breathing devices intended for use in toxic environments should minimize the risk of infiltration of toxic gases or materials into the lungs of a user.
Minimizing the infiltration of contaminants into an air delivery system used by a worker may be difficult due to the development of negative pressures when a worker inhales. Negative pressures developed in breathing masks or other delivery mechanisms may draw contaminants from the surrounding environment into the workers"" air delivery system. The problem of infiltration of contaminants is particularly severe in situations where users engage in strenuous activity while wearing a breathing apparatus. Firefighters are commonly required to work under such conditions.
One approach that has been taken to minimize the risk of infiltration of contaminants into a breathing delivery system is the use of positive pressure breathing devices. Such devices deliver air to the user through a mask that effectively surrounds the user""s nose and mouth. Air is delivered to the user through the mask at a positive pressure above atmospheric. Positive pressure is maintained so that the pressure in the mask is above atmospheric pressure at all times, and particularly while the user is consuming air by inhaling. By maintaining a positive pressure in the mask, any leakage of air will tend to be from the mask to the environment and not vice versa. This reduces the risk that contaminants will infiltrate the mask.
A variety of different approaches have been taken in the past to providing positive pressure in breathing devices. One approach has been to provide a breathing regulator that maintains a positive pressure in the mask at all times. When using a regulator of this type a user dons the mask, opens the regulator to a supply of air and the area in the mask quickly builds to a positive pressure. As the user inhales, air is delivered into the mask in sufficient quantity to maintain a positive pressure. When the user exhales, air from the user""s lungs passes out of the mask through an exhaust valve. The exhaust valve opens at a pressure in excess of that which is maintained in the mask and closes when the pressure falls to the desired positive pressure level.
A problem with breathing devices of this type is that they only operate in a positive pressure condition. The user must control the flow of air to the mask with a manual valve. This poses drawbacks in that it may be difficult to place a valve within a user""s easy reach. If the user must work wearing gloves or other protective equipment on their hands, it may be difficult to provide a valve that is readily manipulated. Another drawback is that a user in an emergency situation, may forget to open the air supply valve until contaminants have been drawn into the mask.
The problems associated with devices that operate only in a positive pressure mode have been reduced by breathing devices which have an xe2x80x9cautomatic-onxe2x80x9d feature. Such breathing devices are capable of being placed in a standby mode in which no air flow occurs when they are off the user""s face. When the user places a mask connected to an automatic-on type regulator device on his or her face and begins breathing, air is delivered to the mask. Once air delivery begins in response to a user""s breathing, pressure in the mask automatically builds to a positive pressure.
Breathing devices which include the automatic-on feature eliminate the need to position a valve that can be manipulated by the user to begin the delivery of air. With automatic-on type devices, air is available as soon as the user begins to breathe. The risk that a user will put on his or her mask while forgetting to open a supply valve is also reduced. This is because the supply valve can remain open even when the breathing device is not planned for immediate use.
When a breathing apparatus that provides positive pressure is removed from the face, significant air will often escape. This is because the regulator operates to attempt to maintain a pressure above atmospheric in a confined space within a mask. As the mask is removed from the user""s face the regulator delivers increasing amounts of air to try to build up a positive pressure until the regulator reaches a full flow condition. This may result in the loss of a significant amount of air until the user manually shuts off the airflow to the regulator.
In the past, mechanisms have been devised for breathing devices that provide automatic-on into positive pressure. These devices also provide for the manual shut off of airflow when the mask is removed from the face. Common mechanisms used for such purposes include toggle and latching levers and catch/release mechanisms. Such mechanisms respond to a user""s inhalation to release a spring to act upon a diaphragm member which causes a valve to deliver air at positive pressure to a user. Such mechanisms must be mechanically re-latched to shut off the air delivery through the regulator.
Such prior art approaches have limitations and drawbacks. The drawbacks can include the limitations associated with the use of complex mechanisms for reliably and predictably releasing a flow of air in response to a user""s inhalation effort.
Prior breathing devices have included a mask and a detachable regulator. In many devices having this configuration the regulator delivers air when the user inhales and provides an outlet path for air exhaled by the user. A regulator which operates in this manner is shown in U.S. Pat. No. 4,361,145. Fluid and condensation in the air exhaled by the user may collect in the regulator. Unless the regulator is disassembled and thoroughly cleaned after each use to eliminate contamination, diseases may be transmitted to subsequent users of the regulator.
Thus, there exists a need for a breathing apparatus for delivering air to a user that reduces contamination, provides automatic on into positive pressure and which conserves air when removed from the face.
It is an object of the present invention to provide a breathing apparatus for delivering air to a user.
It is a further object of the present invention to provide a breathing apparatus for delivering air to a user through a mask which maintains the mask at positive pressure.
It is a further object of the present invention to provide a breathing apparatus for delivering air to a user through a mask that causes the mask to automatically rise to a positive pressure in response to a user""s breathing efforts.
It is a further object of the present invention to provide a breathing apparatus for delivering air to a user that minimizes the loss of air when removed from the user""s face.
It is a further object of the present invention to provide a breathing apparatus which reduces contamination.
It is a further object of the present invention to provide a breathing apparatus for delivering air to a user that is durable and reliable.
Further objects of the present invention will be made apparent in the following Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects are accomplished in the preferred embodiment of the invention by a breathing apparatus for supplying air to a user. The apparatus supplies air to a user at positive pressure in response to changes in pressure that result from a user""s breathing efforts.
The apparatus includes a regulator. The regulator has a body which includes a sensing chamber and a positive pressure chamber. The sensing chamber is connected to the mask and it is exposed to the pressure therein. The pressure in the mask and sensing chamber fluctuates with the user""s inhalation and exhalation. A flexible sensing diaphragm bounds the sensing chamber. The sensing diaphragm moves in response to the changes in pressure in the mask.
An air delivery valve that is connected to a supply of air, is in operative connection with the sensing diaphragm. In the preferred form of the invention the air delivery valve is a main valve that opens and closes in response to the opening and closing of a pilot valve. The sensing diaphragm moves a lever which opens and closes the pilot valve so that the main valve opens in response to a reduction in pressure in the mask caused by the user""s inhalation.
The outlet of the main valve is also in fluid communication with the positive pressure chamber through a check valve. The check valve is oriented so that air may only flow into the positive pressure chamber.
A positive pressure diaphragm bounds the positive pressure chamber. The positive pressure diaphragm moves in a first direction in response to an increase in air pressure in the positive pressure chamber as a result of air passing the check valve. Movement of the positive pressure diaphragm in the first direction operates to bias the sensing diaphragm towards an air delivery position in which the air delivery valve is open.
A manually actuatable vent valve is fluidly connected to the positive pressure chamber. Air pressure in the positive pressure chamber is enabled to be released by actuation of the vent valve.
In one form of the invention the regulator may be releasibly attached directly to a mask. The mask has a mating connector to receive the regulator. In this form of the invention the mask also includes an exhalation valve which enables the passage of air from the facepiece at a predetermined level above atmospheric when the user exhales.
In another form of the invention the regulator is releasibly attached to an adaptor. The adaptor is releasibly attached to the mask. The adaptor includes a chamber which is in connection with the mask. The adaptor also includes an exhalation valve which enables the passage of air out of the adaptor to atmosphere when the pressure in the adaptor chamber exceeds a predetermined level above atmospheric. Both forms of the invention reduce contamination and the risk that diseases will be transmitted between users of the regulator.
In embodiments of the invention the regulator is releasibly connected to the mask. The mask includes a nose cup that covers a user""s nose and mouth. The nose cup includes one or more check valves thereon. The check valve enables flow only from the area in the mask outside the nose cup to the interior of the nose cup, and blocks flow in the opposite direction. Air that is delivered from the air delivery valve of the regulator is delivered into the mask in the area outside the nose cup. In one form of the invention the sensing chamber of the regulator is in communication with the interior of the nose cup. As a result, the nose cup serves as a fluid divider member which in combination with the flow control provided by the check valve enables accurate sensing of the pressure in the mask while air is being delivered thereto. In another form of the invention the sensing chamber is connected to an area outside the nose cup into which the air is delivered.
With the mask and regulator combination off the face, the sensing diaphragm is initially positioned to close a pilot opening of the pilot valve. In this condition no airflow is delivered to the mask. Upon the user donning the mask and inhaling, negative pressure is transmitted to the sensing chamber, moving the sensing diaphragm so as to open the pilot valve. The opening of the pilot valve creates a pressure differential across a valve disk element of the main valve. This causes the main valve to open.
The main valve delivers air both to the mask as well as to the positive pressure chamber. The increased pressure in the positive pressure chamber moves the positive pressure diaphragm to apply a biasing force to the sensing diaphragm. The application of the biasing force biases the sensing diaphragm toward a valve opening position. As a result, air is delivered into the mask until a positive pressure is achieved therein.
Exhalation by the user wearing the mask causes the pressure in the mask to reach a higher level due to exhalation pressure. This elevated pressure in the mask opens the exhalation valve. The exhalation valve remains open until the user stops exhalation. The exhalation valve closes at a pressure above atmospheric to maintain positive pressure in the mask.